Terpolymers of ethylene,a vinyl ester and an unsaturated amide



3,451,982 TERPOLYMERS F ETHYLENE, A VINYL ESTER AND AN UNSATURATED AMIDE George A. Mortimer, La Marque, Tex., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Aug. 4, 1965, Ser. No. 477,306 Int. Cl. C08f 15/40 U.S. Cl. 260-8073 6 Claims ABSTRACT OF THE DISCLOSURE Substantially random addition terpolymers of ethylene, a vinyl ester and an unsaturated amide prepared by polymerizing the monomers at elevated temperatures and pres sures in the presence of a free-radical-generating catalyst.

The present invention relates to new polymeric compositions and, more particularly, to interpolymers of ethylene with vinyl esters and polymerizable unsubstituted and substituted acrylamides and methacrylamides and to a method for their preparation.

High-molecular-weight solid polymers of ethylene are well known in the art. These polymers have a wide range of physical characteristics and chemical properties which make them useful for many purposes. They can be produced by subjecting ethylene to polymerization at elevated pressures from 5,000 to 60,000 p.s.i.g. and elevated temperatures from 100 to 400 C. in the presence of freeradical initiators for the polymerization reaction. The properties of the polymers can be tailored, so to speak, to a degree by varying polymerization conditions, using different initiators, etc. Variation in polymer properties such as density, molecular weight, melt index, tensile strength, stiffness and surface appearance can also be obtained by the use of compounds known as modifiers in the polymerization reaction and/or by polymerizing the ethylene with small amounts of comonomers. It has been proposed heretofore, for example, to polymerize ethylene in admixture with vinyl esters such as vinyl acetate, for example, to produce polymeric products which are tougher than polyethylene and from which thin blown films can be made which have less haze than do thin films of polyethylene. While the resulting copolymers are satisfactory for some purposes, they are inadequate for others because of their lack of the requisite toughness and stiffness. It has now been discovered that the addition of certain unsubstituted or substituted acrylamides and methacrylamides as a third component in ethylene-vinyl ester polymer compositions results in a polymeric product which is tougher than ethylene-ester copolymers. Thick specimens of the ethylene-ester-acrylamide terpolymers have a transparency substantially equivalent to polyethylene films whereas specimens of polyethylene and ethylene-ester copolymers of comparable thickness are opaque. The terpolymers are also stitfer than the prior art copolymers when a sufficient amount of the amide component is present. Particularly noteworthy is the enhanced stiffness since ordinarily only small amounts-of the vinyl esters can be polymerized with ethylene to obtain the desired modified properties in the resulting polymer. Use of amounts outside the rather narrow ranges disclosed as suitable adversely affects the rigidity of the polymers leading to rubberlike materials.

It is, accordingly, an object of the present invention to provide novel, solid interpolymers of ethylene characterized by a high degree of toughness and yet possessing a stiffness either equivalent to or superior to that of polyethylene and prior art copolymers. Another object of the nited States Patent 0 invention is to provide stitf, tough interpolymers of ethylene which are characterized by high transparency and are eminently suitable for use in the production of bottles, films and molded objects.

These and other objects and advantages of the invention which will become apparent from the following description thereof are accomplished by interpolymerizing ethylene, a vinyl ester of a saturated monocarboxylic acid containing up to 20 carbon atoms, and an amide of the formula wherein R may be hydrogen or a methyl radical and R may be hydrogen or an alkyl, hydroxyalkyl or aryl radical having up to 8 carbon atoms.

As examples of the vinyl esters which can be interpolymerized with ethylene and the defined amide compound to produce the novel and improved interpolymers of the invention, there may be mentioned vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl crotonate, vinyl linoleate,

vinyl pivalate, vinyl trifiuoroacetate, and the like.

Specific examples of the amides useful as the third monomer for producing the interpolymers of the inven-. tion include acrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, N-amylacrylamide, N-tert-octylacrylamide, N-decylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, N-hydroxypropylacrylamide, N-phenyl-acrylamide, N-o-tolylacrylamide, N-ptolylacrylamide, N-naphthylacrylamide, and the like as well as methacrylamide and all of the corresponding substituted methacrylamides.

-In general, the interpolymers of the invention should contain at least mole percent ethylene. Usually, amounts of ethylene from about 60 to about 98.5% are employed with amounts from about 80 to about 98 mole percent being preferred. The vinyl ester is present in amounts from about 1 to about 20 mole percent with amounts in the range from 1 to 10 mole percent being preferred. The amount of the unsaturated amide which constitutes the third component of the novel interpolymers of the invention may vary from about 0.5 to about 20 mole percent but preferably the quantity of the amide comonomer is from about 1 to about 10 mole percent.

The polymerization process by which the interpolymers are produced is conducted at superatmospheric pressures from about 5,000 p.s.i.g. up to as high as 60,000 p.s.i.g. Preferably, the pressures employed are in the range from about 20,000 to about 35,000 p.s.i.g.

While the temperature of the polymerization process may be varied over the range from about to about 400 0, preferred temperatures are those from about to about 300 C.

Any of the well known free-radical initiators used for catalyzing the polymerization of ethylene can be employed for producing the novel interpolymers herein described. Among these may be mentioned molecular oxygen; per-oxygen type compounds such as hydrogen peroxide, dialkyl dioxides such as diethyl peroxide and di-tert-butyl peroxide, diacyl peroxides such as lauroyl peroxide and benzoyl peroxide, alkyl hydroperoxides such as tert-butyl hydroperoxide, diperoxy dicarbonate esters such as diisopropylperoxy dicarbon-ate, tert-alkyl percarboxylates such as tert-butylperbenzoate, persulfates such as potassium persulfate, peracids such as peracetic acid and the like; azo-type compounds such as azo bis-isobutyronitrile; azines such as benzalazine; oximes such as acetone oxime; etc. Particularly suitable are peroxides such as di-tert-butyl peroxide, for example. Only small amounts of the initiator are required. Generally, initiator concentration will vary from about 0.0005 to about 2% of the total weight of the monomers charged to the 4 pressure reached about 7500 p.s.i. at the temperature level of 130 C. Then the mechanical agitator inside the bomb was activated and the normally liquid feeds, i.e., the comonomers contained in a solvent vehicle, and ditert-butyl peroxide initiator dissolved in benzene, were polymerization reactor. 5 forced from a small cold compartment of the bomb where So-called polymerization modifiers or chain-transfer they had been stored free of air or oxygen contamination agents can also be employed in the manufacture of the into the reaction chamber by means of high pressure interpolymers of the invention, if desired, to obtain cerethylene charged until a final pressure of 20,000 psi. at tain polymer properties which such modifiers or chain- 130 C. was attained. After the desired reaction time, the transfer agents may impart. Examples of compounds in bomb was depressurized and the polymer product was regeneral used in the art for this purpose are aliphatic covered and its physical properties determined. alcohols containing one to ten carbon atoms and prefer- A summary of the reaction conditions for the various ably three to five carbon atoms such as methanol, proruns made is presented in Table T below and the physical panol, isobutanol, hexanol and decanol; aliphatic satuproperties determined for the interpolymers produced rated ketones containing three to ten carbon atoms and under these conditions are presented in Table II. The preferably three to five carbon atoms such as acetone, methods used for the determination of melt index and diethyl ketone, methyl isopropyl ketone and the like; density are described in J. App. Polymer Sci., 8, 839 saturated aliphatic aldehydes containing one to eight (1964) and J. Polymer Sci., A2, 1301 (1964), respeccarbon atoms and preferably two to five carbon atoms tively. All other evaluations were performed on nominally such as formaldehyde, acetaldehyde, butyraldehyde and ZO-mil thick specimens. A standard procedure, ASTM the like; saturated hydrocarbons such as ethane, propane, D-l822 61T, was followed for the tensile impact test cyclohexane and the like; aromatic hydrocarbons such as using the S specimen. The L specimen of this procedure toluene, xylene and the like; chlorinated hydrocarbons was used for slow speed testing. It was pulled at 2 in./ min. such as chloroform, carbon tetrachloride and the like; and in an Instron tensile testing machine until the sample hydfogehfailed. From the force curve, the modulus (5% secant), The polymerization process may be either a batch or a tensile at yield, and tensile at fail were calculated based continuous one. The preferred method is the continuous on the dimensions of the unextended specimen. Haze was type of operation wherein ethylene, the vinyl ester conionalso determined on 20-mil specimens using Procedure A omer, the amide comonomer, initiator, and modifier, if of ASTM Dl0036l defining haze as diffuse luminous one is used, are charged to a reactor maintained under transmittance where a lower value indicates a less hazy, suitable conditions of temperature and pressure, intermore transparent sample. polymer is continuously separated from the reactor efllu- Vinyl acetate content of the polymers was calculated ent, and unreacted monomers, initiator, and modifier, if from the reactivity ratios reported by Brown and Ham, any, are recycled to the reactor. I. Polymer Sci., 42, 3623 (1964) and Burkhart and Zutty, The invention is illustrated in the following example I. Polymer Sci., 41, 1137 (1963). The content of the other which, however, is not to be construed as limiting it in esters and of the amides was determined either by comy manna whatsoever- A11 Percentages given therein are bust ion elemental analysis or by scintillation counting if on a molar basis unless otherwise indicated, except con th er w C -label d. Version which is given in Weight Percent 40 :It will be seen from the first four runs in Table II that EXAMPLE the incorporation of an acrylic-type amide into an ethylone-vinyl acetate copolymer permits the attainment of A Sens? of expenmlfms conqucted Whlch ethylproperties in the resulting interpolymer unobtainable ene was rnterpolymenzed with various vinyl esters and f I th 16 with vi 1 acetate as both unsubstituted and substituted acrylamides. In each 9 yme.nZmg e y ne ny experiment, a steel reaction bomb together with all accesmed m the pnol: Thfi terpolymers have l St Hess sory lines thereto was carefully cleaned and flushed with lowconteht Vinyl acetate P Ym IS, the impact reethylene to eliminate an traces 0f air or oxygen The sistance of higher content vinyl acetate copolymers, and normally gaseous f ed materials, i.e., ethylene and proultimate strength and transparency superior to that of pane which was used as a modifier, were introduced into known y W acetate copolymers- The Polymenc the reaction chamber of the bomb heated to the reaction P Odllcts Obtained y ihterpolymerilatioh of different other temperature of 130 C. at atmospheric pressure until th unsaturated amides with other vinyl esters and ethylene pressure increased to about 700 p.s.i. Thereafter, addilikewise exhibit comparable enhanced properties over the tional hot ethylene was pumped into the bomb until the known related copolymers.

TABLE I Feed Composition Con- Initietor Ben- Cone, zene, CaHg, Reaction wt. moles/ii. C1114, Per- Per- CHaOH, perpertime per- (x10- percent Vinyl Ester cent; Amide cent percent cent cent (min) cent 2.1 82.3 Vinyl acetate 1.0 0.2 16.6 52 9.5 2.1 82.4 4.1 0.2 13.4 50 a3 4.1 1.0 N-isopropylaerylamida. 1.1 13.4 28 6.1 4.1 1.0 N-phenylacrylamide. 0.2 13.4 114 12.3 4.1 0.7 0.2 14.4 47 7.1 6.2 1.7 0.2 8.0 74 0.3 5.2 0.7 0.1 83 7.2 2.1 0.6 0.2 16.6 63 10.1 4.1 0.0 0.2 16.6 45 5.8 2.1 1.0 0.2 14.4 as 8.9 6.2 1.9 0.2 13.9 as 4.1 0.8 1.8 5.3 50 8.3 4.1 0.2 5.3 73 8.8

0. 8 Acrylamide 4.9% e hanol used as modifier in thisrun. 0.5% 10.

TABLE II Polymer Composition, Tensile percent Melt at Tensile Tensile Index Modulus, Density, Yield, at Fail, Impact, Haze, C Hi Ester Amide (dg./min.) p.s.i. gJcc. p.s.i. p.s.i. p.s.i. percent Polymer from Run No.2

98.8 1. 2 4. 7 1, 390 0. 938 1, 630 2, 040 54 72 95. 3 4. 7 4. 8 700 0. 941 960 3, 120 304 49 96. 8 1.3 3. 1 1, 220 0. 935 1,330 4, 270 310 5 96. 9 1. 5 2. 7 1, 350 0. 946 1, 560 3, 120 192 46 98. 9 1.1 3.0 1, 880 937 2, 050 2, 860 54 71 98v 1 1. 9 l1. 4 1, 380 0. 938 1, 560 2, 300 64 65 94. 1 1. 3 4. l 1 1, 930 0.933 1, 640 5, 370 331 4 99. 1 0. 9 3. 2 1, 530 0. 932 1, 760 2, 920 83 97. 8 1. 0 0. 9 1, 430 0 936 1, 690 2, 820 95 71 97. 6 2. 4 1. 8 910 0 930 1, 130 4, 220 521 72 92. 8 3. 0 1. 7 1, 010 0 933 1, 180 5, 270 344 12 98. s 1. 2 0. 6 1, 670 0. 936 1,820 1, 820 130 97. 2 1. 4 1. 4 0. 8 1, 380 0. 935 1, 620 3 470 220 72 1 When the modulus exceeds the tensile at yield, the initial portion of the stress-strain curve must be extrapolated to elongation to measure the molulus. 2 Not measured.

The interpolymers of the invention are useful per se in many applications or they may also be blended with other thermoplastic polymers to produce films, moldings, bottles and the like. Fillers, reinforcing agents such as fibrous materials and foaming agents may be added to the interpolymers to render them suitable for particular applications. The properties of the interpolymers can be preserved or enhanced by the addition of stabilizing agents and pigments may be added to the interpolymers to obtain colored compositions.

What is claimed is:

1. Substantially random addition interpolymers consisting essentially of from about 60 to about 98.5 mole percent ethylene, from about 1 to about 20 mole percent of a vinyl ester of a saturated monocarboxylic acid containing up to 20 carbon atoms, and from about 0.5 to about 20 mole percent of an amide of the formula wherein R is selected from the group consisting of hydrogen and the methyl radical and R is selected from the group consisting of alkyl, hydroxyalkyl and aryl radicals containing up to 8 carbon atoms.

2. Substantially random addition interpolymers consisting essentially of from about 80 to about 98 mole percent ethylene, from about 1 to about 10 mole percent of a vinyl ester of a saturated monocarboxylic acid containing up to 20 carbon atoms, and from about 1 to about 10 mole percent of an amide of the formula References Cited UNITED STATES PATENTS 3,405,200 10/1968 Yasumura 260-897 2,396,785 3/ 1946 Hanford 260-78 3,232,895 2/1966 Klein et a1. 260-80.73 2,450,451 10/ 1948 Schmerling 26094.9 3,380,851 4/1968 Lindemann 117-14O JOSEPH L. SCHOFER, Primary Examiner. ROGER S. BENJAMIN, Assistant Examiner.

U.S. Cl. X.R. 260-8081 

